One assignee leads the field clearly, holding 58 of the 201 records in scope, which is roughly five times the count held by the fifth-ranked company. The top 5 assignees combined account for 68.7% of all records, and the top 10 reach 87.1%, so the field is concentrated at the top with a long tail of smaller filers below it. The ranking published for this dataset covers 30 companies in total, most of them holding only a handful of filings each.

Filings moved from 2 records in 2021 to 54 in 2024, a 2,600% increase over that three-year span, following several years of near-zero activity from 2017 through 2020. The dataset does not attribute a specific cause to this shift, but the timing coincides with broader industrial decarbonisation and waste-heat recovery investment during that period. Readers should treat 2024 as the most recent complete year for trend purposes, since publication lag means 2025 and 2026 figures are still filling in.

Chemistry-related claims are more heavily represented: C09K, covering materials for miscellaneous applications including refrigerants, appears in 53.7% of the 201 records, compared with 31.8% for F25B, the refrigeration and heat-pump hardware class. This does not mean mechanical design is unimportant, but it does mean the claim space around working-fluid composition is more densely occupied than the claim space around compressor, cycle or heat-exchanger architecture. A filer targeting hardware architecture is working against comparatively thinner prior art in this dataset.